1. Field of the Invention
The present invention generally relates to a dielectrophoretic particle concentrator and a concentration with detection method, and more particularly, to a dielectrophoretic particle concentrator and concentration with detection method having high efficiency.
2. Description of Related Art
In our lives, a number of trace germs exists in food and drinking water. In fact, the medical blood testing and urine testing are also conducted targeting many items of trace germs. Many of the biochips developed in recent years are designed to simplify the processes of trace measurement, among which a dielectrophoresis mechanism (DEP mechanism) is used to concentrate the trace particles in a specimen fluid so as to facilitate the measurements. Particles with different dielectric properties act under dielectrophoresis force (DEP force) so that the drifted and floating particles in a flowing fluid are gathered at a detection region to be detected.
The above-mentioned DEP force appears due to an existing electrical field gradient, i.e., the DEP force is produced under an environment with a non-uniformed electrical field. FIG. 1 is a diagram showing the dielectrophoresis mechanism. Referring to FIG. 1(a), a flat-plate electrode 64 and a localized electrode 62 herein are applied by a voltage of an AC power or a DC power. Since the flat-plate electrode 64 and the localized electrode 62 are asymmetric with each other, a non-uniformed electrical field 60 is formed. The localized electrode 62 and the flat-plate electrode 64 respectively take, for example, a positive level and a negative level, the electrical field lines of the electrical field 60 are non-uniformed, and the closer to the localized electrode 62, the stronger the electrical field is. For the dielectric particles able to produce a positive electrophoresis force (p-DEP force), the negative charge end thereof is closer to the localized electrode 62 and the positive charge end thereof is closer to the flat-plate electrode 64. Due to the difference of the electrical field intensity, an attractive force of the localized electrode 62 on the upper end has a direction shown by the bold arrow and is greater than the attractive force of the flat-plate electrode 64 on the lower end. As a result, the p-DEP particles move upwards.
Contrarily as shown by FIG. 1(b), for the dielectric particles able to produce a negative electrophoresis force (n-DEP force), the negative charge end thereof is closer to the flat-plate electrode 64 and the positive charge end thereof is closer to the localized electrode 62. At the time, a repulsion force of the localized electrode 62 on the upper end has a direction shown by the bold arrow and is greater than the rejective force of the flat-plate electrode 64 on the lower end. As a result, the n-DEP particles move downwards. In terms of an AC voltage, corresponding to the next phase of the electrical field, it is also a non-uniformed electrical field to move the dielectrophoretic particles. In this way, the dielectrophoretic particles can be separated and concentrated by means of the DEP force.
Although the DEP force has been used to detect trace particles and find its applications, but the project of how to more effectively concentrate the trace particles by using the DEP force is still being developed.